1. Technical Field
This invention relates to a magnetic recording medium, more particularly, to a magnetic recording medium for use in magnetic read/write equipment such as magnetic disk equipment known as hard disk drives (HDD), and further particularly, to the structure of a magnetic recording medium having a high recording density.
2. Background Art
High-capacity storage devices, especially hard disk drives featuring a high data transfer rate, quick access, high reliability and low price have marked a significant advance toward higher capacity and higher density. An improvement in areal recording density is accomplished by miniaturizing recording magnetic domains formed in the magnetic recording layer. At present, the density has exceeded 5 gigabits per square inch, with development efforts being made with the target on 10 gigabits to 100 gigabits.
Used as the magnetic head for write and read operation is a combined magnetic head in which an inductive head as the write head is combined with a magnetoresistive head (MR head) as the read head, which are mounted on a slider. Since the output of the MR head is determined by a magnetic flux change per circumferential unit length, in principle, the output does not decline even when the track width is minimized. The use of the MR head thus suggests a possibility to realize narrow tracks. The same applies to a giant magnetoresistive head (GMR head) with which a higher recording density is expected.
However, if the track width is too narrow, the interference or crosstalk between magnetic signals from adjacent recording tracks increases so that the degradation of read signals becomes a problem.
The areal recording density can also be increased by reducing the recording bit length. If the recording bit length is too short, the interference or partial erasure between magnetic signals from adjacent bits increases so that the degradation of read signals becomes a problem.
JP-A 9-297918 discloses a magnetic recording medium in which a plurality of recording portions are provided in the form of rectangular regions having two side lengths equal to a track width and a minimum bit-determining length, the plurality of recording portions are separated by space areas, and information is stored in the recording portions. This medium is a so-called patterned medium. The patterned medium is effective for suppressing the degradation of read signals by crosstalk and partial erasure.
A magnetic disk device utilizing the contact-start-and-stop (CSS) system has the risk that the slider of the magnetic head, which is in contact with the magnetic disk at rest, can stick to the disk at start-up to disrupt the recorded information. To prevent the sticking of the slider is an outstanding problem.
For preventing the slider sticking phenomenon from occurring in the magnetic disk device of the CSS system, it is contemplated effective to provide the disk surface with minute protrusions and depressions. Such minute protrusions and depressions reduce the contact area of the disk surface with the slider, reducing the sticking force.
For example, JP-A 2-156417 describes that a coating layer of a gel containing inorganic particles having a large particle size and inorganic particles having a small particle size is formed on a substrate before a magnetic layer is formed thereon. Those particles having a large particle size protrude from the coating layer to provide the magnetic disk surface with protrusions and depressions, preventing the slider from sticking thereto.
Also, JP-A 5-234070 proposes a medium having protrusions on its surface wherein an alumilite coating is formed on the surface of a substrate, the alumilite coating is treated with a fluorine-containing solution or gas, or a solution selected from among acids, bases, and salts of strong acids, and a magnetic film is then formed.
As discussed above, the prior art requires to employ an independent step for providing the medium surface with protrusions and depressions, resulting in a drop of productivity. For the patterned medium, effective means for preventing the slider from sticking to the medium has not been proposed.
In conjunction with a so-called patterned medium comprising recording tracks each having an array of unit minute recording portions of a magnetic material separated by non-recording portions of a nonmagnetic material, an object of the invention is to prevent a magnetic head slider from sticking to the medium.
This and other objects are attained by the present invention which is defined below.
(1) A magnetic recording medium comprising recording tracks each having an array of unit minute recording portions of a magnetic material separated by non-recording portions of a nonmagnetic material, the unit minute recording portions having a higher surface height than the non-recording portions.
(2) The magnetic recording medium of (1) wherein the surface height of the unit minute recording portions is 5 to 30 nm higher than the surface height of the non-recording portions.
(3) The magnetic recording medium of (1) wherein each unit minute recording portion is a single magnetic domain.
(4) The magnetic recording medium of (1) wherein the unit minute recording portions are constructed of any one of Co, Coxe2x80x94Cr, Coxe2x80x94Crxe2x80x94Ta and Coxe2x80x94Crxe2x80x94Pt.
Since the surface height of the unit minute recording portions is set higher than the surface height of the non-recording portions according to the invention, the unit minute recording portions and non-recording portions form protrusions and depressions which prevent the slider from sticking to the medium. The invention eliminates a need for an extra step for providing the medium surface with depressions and protrusions.